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V & C Core Concept 5: Systems

An ecologist observes the diet of a bird species consists primarily of large grass seeds, less on medium seeds and nearly no small seeds. She hypothesizes that birds choose the larger seeds because they have a higher concentration of protein than smaller seeds. To test this hypothesis, she analyzes protein content of the seeds and indeed finds that large seeds have a higher concentration of protein than medium or small seeds.

Average ocean temperatures have risen 0.5° C in the last 40 years. While this seems like an insignificant change, climate scientists are very alarmed. How would a scientist use the properties of water to justify this temperature increase as a serious driver of climate change?

Albacore tuna and other ocean predator fish are far removed from any direct source of pollution, yet their tissues frequently have dangerously high levels of mercury (a heavy metal that is particularly dangerous to children, pregnant women, and the elderly). How might a biologist explain how this chemical has reached such high levels in these animals?

Polar bears are far removed from any direct source of pollution, yet their tissues and milk have some of the highest levels of PCBs (an industrial pollutant that disrupts hormones, damages internal organs and causes cancer) of any mammal on Earth. How would a biologist explain how this chemical has reached such high levels in these animals?

Prairie dogs are small burrowing mammals native to North American grasslands. They live in colonies and forage above and below ground for seeds and insects. Ecologists have labeled prairie dogs as a keystone species, a species that is critical to maintaining high levels of species diversity in a community. Imagine a farmer in Kansas kills all the prairie dogs on his farm because he didn’t like “molehills.” Predict the likely outcome in this grassland community when prairie dogs are removed.

In North America, prevailing winds typically move from west to east. On the Pacific coast, there are two significant mountain ranges, the Sierra Nevada Mountains in California, and the Cascade Mountains in Oregon and Washington, that both run generally north to south. Describe how these mountains result in a rain shadow effect where the western slopes of these mountain ranges receive more precipitation than the drier eastern slopes.

“Trophy hunting” is the hunting of wild game animals for human recreation; the “trophy” is the part of the animal that is kept and displayed. Trophy hunters usually try to take the biggest and showiest animals of a population. This practice has shown dramatic long-term effects on the population structure of game animals. Assume that trophy hunting, while removing some individuals from a population, does not drive the population to extinction. Predict at least two long term outcomes of trophy hunting on game animal populations.

Consider a pond where two species of phytoplankton (algae), A and B, live. Both species need phosphorus to grow, and there is not enough phosphorus in the pond for both species to grow indefinitely. Over time, species A and B both remained in the pond, with A more abundant than B. How would a biologist explain why this happened? (Note: neither species consumes the other species.)